The technical portion of the work carried out by an optician consists in mounting a pair of ophthalmic lenses in or on the frame selected by the user, in such a manner that each lens is suitably positioned facing the corresponding eye of the user so as to perform as well as possible the optical function for which it is designed. In order to do this, it is necessary to perform a certain number of operations.
After the frame has been selected, the optician must begin by situating the position of the pupil of each eye in the frame of reference of the frame. The optician thus determines mainly two parameters that are associated with the morphology of the user, namely the pupillary distance and the height of the pupil relative to the frame.
For the frame itself, it is necessary to identify its shape, and this is generally done by means of a pattern or an apparatus specially designed to read the inner contour of the rim (i.e. the part of the frame that goes round the lens), or else from an electronic file that is prerecorded or supplied by the manufacturer.
From the above geometrical input data, it is necessary to cut each lens to shape. A lens is cut to shape for mounting in or on the frame selected by the future user by modifying the outline of the lens so as to match it to that of the frame and/or to the shape desired for the lens. Cutting to shape comprises an edging operation for shaping the periphery of the lens, and depending on whether the frame is of the rimmed type or of the rimless type with local clamping through fastener holes formed in the lens, appropriately beveling and/or drilling the lens. Edging (or cutting out proper) consists in eliminating the superfluous peripheral portion of the ophthalmic lens in question so as to reduce its outline, which is usually initially circular, to the arbitrary outline of the rim or surround of the eyeglasses frame in question, or merely to the pleasing shape desired when the frame is of the rimless type. This edging operation is usually followed by a chamfering operation which consists in dulling or chamfering the two sharp edges around the edged lens. When the frame is of the rimmed type, the chamfering is accompanied by beveling which consists in forming a rib usually referred to as a bevel, generally of triangular cross-section with a top that is rounded or interrupted by a counter-bevel on the edge face of the ophthalmic lens. The bevel is for engaging in a corresponding groove, also known as a bezel, formed in the rim or the surround of the eyeglasses frame in which the lens is to be mounted. When the frame is of the rimless type, the cutting out of the lens and optionally the dulling of its sharp edges (chamfering) are followed by appropriately drilling the lenses to enable it to be secured to the temples and to the bridge of the rimless frame. Finally, when the mounting is of the type having a rim of Nylon string, the chamfering is accompanied by grooving consisting in forming a groove in the edge face of the lens, the groove being for receiving the mounting Nylon string for pressing the lens against the rigid portion of the frame.
Usually, these edging, chamfering, and beveling operations are performed in succession on a single machine tool, known as an “edger” and provided with a set of suitable cutter/grinder bits. Drilling can be performed on the edger which is then fitted with corresponding drill bits, or else on a separate drilling machine.
The optician must also perform a certain number of measurement and/or identification operations on the lens itself prior to cutting out in order to identify certain characteristics such as, for example: the optical center if the lens is a single-vision lens or the mounting cross if the lens is a progressive lens, or the direction of the axis of progression and the position of the centering point if the lens is a progressive lens. In practice, the optician marks certain characteristic points using a marker tip on the ophthalmic lens itself. These marks are used for securing a chuck receiver or centering-and-drive pad on the lens enabling the ophthalmic lens to be positioned correctly in the edger that is to give it the desired outline, corresponding to the shape of the selected frame. The pad is usually stuck temporarily on the lens by means of a double-sided adhesive. This operation is commonly referred to as “centering” the lens, or by extension, “blocking” the lens, insofar as the pad can be used subsequently for blocking purposes, i.e. for preventing the lens from moving relative to the means for cutting it to shape in a geometrical configuration that is known because of the pad.
Various measurement and identification devices are known that operate either automatically or manually, to measure various characteristics, in particular centering or identification characteristics, of a single-vision or progressive ophthalmic lens, before or after mounting on a frame. One such device is known in particular from document FR-2 825 466 having as its equivalent US-2003/0015649 published on Jan. 23, 2003.
After the centering pad has been put into place, the lens fitted in this way is then placed in the cutting-out machine where it is given the shape that corresponds to the shape of the selected frame. The centering pad serves to define and physically to embody on the lens both a geometrical frame of reference in which characteristic points and directions of the lens are identified, with this being necessary for the lens to be positioned properly relative to the pupil, and also cutting out values for ensuring that these characteristic points and directions are properly positioned in the frame.
Depending on the organization and the equipment available to the optician, the above-mentioned operations can be spread over two or three distinct workstations. Each lens being processed must therefore be transferred from one workstation to another. Inaccuracies, errors, or accidents can then arise because of the large amount of handling. In addition, if the operations are performed in the context of an industrial organization, that gives to a considerable loss of time and to high production costs. In addition, the risk of damaging the ophthalmic lens increases with the amount of handling, thereby considerably lengthening time to delivery and further increasing costs.
Document FR 2 825 308 and its equivalent EP 1 392 472 propose optimizing the above-specified process by automating some of the measurement and positioning stages applied to the ophthalmic lens, thus making it possible to determine the optical characteristics of the lens and to control the stage of transporting said lens to the cutting-out station and the cutting-out stage proper.
The device proposed therein comprises means for measuring identification characteristics of said lens and means for cutting said lens to shape, enabling the outline of the lens to be brought to the desired shape. Conventionally, the cutting-out means are constituted by an edger which has a set of grindwheels and means for blocking and driving the lens in rotation constituted by two rotary shafts on the same axis mounted to move axially to pinch the lens on its axis like a clamp. To enable the lens to be moved towards or away from the grindwheels while machining is taking place, the clamping and drive shafts are carried by a transversely-movable rocker (movable in pivoting or in translation). Partial automation of the process of preparing the lens is obtained by a sliding reception and transfer carriage arranged to transfer the ophthalmic lens through two transfers between three positions, with transfer from a measurement position in which the ophthalmic lens is presented to the measurement means to an intermediate position distinct from the measurement position, and then transfer from said intermediate position to a cutting-out position distinct from the intermediate and measurement positions.
However in that device, the receiver and first transfer means for the lenses take charge of only one lens at a time. In addition, the arrangement of those means in the form of a sliding carriage with the lens being taken directly by the rocker of the edger do not make it possible to envisage a plurality of lenses being taken in charge simultaneously, without that leading to a significant increase in the size of the device and its processing time. The use of a sliding carriage as second transfer means also runs the risk of raising problems associated with accuracy, size, and cost.
Furthermore, in that device, the operator loads the lens onto the carriage at the measurement position before it is measured, and also unloads the lens from the carriage at the intermediate position after it has been cut out, without there being any protection at the measurement or intermediate positions, such that the loading and unloading of the lenses onto and from the carriage relies firstly on the initiative and goodwill of the operator (who must determine whether the processing of the lens is ongoing or has terminated), and also assumes that there is direct access to the measurement device, which makes it vulnerable to all kinds of external attack, and in particular to being dirtied, and furthermore requires access to the lens in the intermediate position even though it is essential in that position to preserve the lens from any untimely displacement. Unfortunately, separating the loading position from the intermediate position would not appear to be possible at present without increasing the size of the device as a whole and degrading its performance and/or allowing its cost to drift.